N-methyl or N,N-dimethyl amines are important part of N-alkylated amines and widely used in the field of chemistry, chemical industry and pesticides production. For example, N-methylaniline can be used for producing novel pesticides and insecticides such as buprofezin, methyldimuron, anilinephenobenzuron, latifolinine etc.; for producing dye intermediates such as N-methyl-N-benzylaniline and N-methyl-N-hydroxyethylaniline etc.; for producing rubber ingredients such as zinc methylphenyldithioaminoformate, dithiodimethyldiphenylthiuram; and also for producing deterrent in nitroglycerin powder, i.e. N-methyl-N-phenylaminoformyl chloride. Also, typical N,N-dimethylaniline is useful for producing perfumes such as vanillin; basic dyes such as basic flavine, basic violet 5BN, basic turquoise blue BB etc., and key intermediates of sulfonylureas herbicide, such as 2-amino-4,6-dichloropyrimidine etc.
It is well known that amines can be produced at low cost on a large scale, and the modern industrial production techniques of amines have been established. At present, alkylation reaction of amines with methanol is a main production route of N-methyl or N,N-dimethyl amines and is widely used in the industrial production of N-methyl or N,N-dimethyl amines. As a regenerable source, carbon dioxide has a giant advantage, namely it has rich reserves and no toxity. However, commercialization of this technique is limited by the current high cost and low efficiency in the chemical fixation technique of carbon dioxide. Since early 20th century, many studies have been performed on the chemical utilization of carbon dioxide and have achieved a series of progress. Among them, the most important chemical utilization process of carbon dioxide is the production of urea via the reaction between carbon dioxide and ammonia gas. In the meantime, carbon dioxide is also utilized well in the field of cyclic carbonate, polycarbonate materials production etc. Recently, the production of N-methylation or N,N-dimethylation is also achieved by using carbon dioxide as the methylating agent carbon source and silicanes as reducing agent (Chem. Sci., 2013, 4, 2127; Angew. Chem. Int. Ed., 2013, DOI: 10.1002/ anie.201301349). However, the use of silicanes as reducing agent results high production cost and difficult separation of the products, so that it cannot be applied on large scale. Hydrogen gas is currently the cleanest and cheapest reducing agent, thus the production of N-methyl or N,N-dimethyl amines by using carbon dioxide as the methylating carbon source and hydrogen gas as the reducing agent certainly has more excellent economical efficiency and environmental friendship.
Accordingly, for the purpose of industrial application, there is a strong need for developing a production process of N-methyl or N,N-dimethyl amines, in which carbon dioxide is used as the methylating carbon source and hydrogen gas as the reducing agent.